Thermal unrest of a fumarolic field tracked using VIIRS imaging bands: The case of La fossa crater (Vulcano Island, Italy)

Abstract

Detecting precursory signals before an eruption is one of the main objectives of applied volcanology. Among these signals, the variation of the emitted heat flux is certainly an important indicator of a state of disequilibrium within the magmatic system. Here we report the results of a detailed analysis of VIIRS (Visible Infrared Imaging Radiometer Suite) imaging bands (at 375 m spatial resolution) focused on measuring the Volcanic Radiative Power (VRP) emitted by the fumarole field of La Fossa crater (Vulcano Island, Italy) over the past decade (2012–2022). The analysis reveals that the long-term, steady-state VRP (baseline ∼0.17 MW) was perturbed in 2020–2021 when a prolonged period of lower than normal (<-2σ) radiant flux preceded the major unrest phase that began in mid-September 2021. By early October the anomalous VRP had peaked at ∼1.2 MW (6–8 times the baseline) then started to gradually decline in the following months. A subsequent thermal pulse was recorded in May–July 2022 and was accompanied by a period of seawater discoloration that affected the Baia di Levante (a shallow sea bay ∼1.4 km north of La Fossa crater). The concomitance of these phenomena suggests the occurrence of a second pressurization phase driven by the arrival of deep magmatic fluids within both the central and distal degassing fumarolic zones. These results provide a complementary, important contribution to the understanding of the unrest of La Fossa crater and highlight the potential of VIIRS in detecting pre-eruptive signals at other poorly-monitored volcanoes characterized by high-temperature fumarolic activity.

Anatomy of thermal unrest at a hydrothermal system: Case study of the 2021-2022 crisis at Vulcano

“…16a). These estimations are consistent with the VIIRS derived radiative heat ux obtained by Coppola et al (2022) i.e. 1.2 MW, with theirs values targeting only the fumarole eld.…”

“…With a swath width of 3060 km in a near-circular, sun-synchronous, near-polar orbit, at 840 km mean altitude, VIIRS provides data every 12h, or less depending on the latitude, in 22 spectral bands from 412 nm to 12 µm of which: 5 (I-bands) at 375 m at Nadir, 16 (M-bands) at 750 m at Nadir and one day/night panchromatic band at 750 m spatial resolution throughout the scan respectively (Wolfe et al 2013). Among these bands, the higher spatial resolution middle infrared band, I04 (centered at 3.74 µm) and the thermal infrared band I05 (centered at 11.45 µm) at 375 m are particularly useful for the monitoring of subtle thermal anomalies observable in closed conduit volcanos (Coppola et al 2022). VIIRS archive imagery can be searched and downloaded via the NOAA CLASS Data web interface (https://www.avl.class.noaa.gov/) or automatically downloaded by using the wget utility via the Lance Near Real Time system, generally available within three-to-ve hours from the satellite observation.…”

Detection of Subtle Thermal Anomalies: Deep Learning Applied to the ASTER Global Volcano Dataset

“…12). This trend is [27] and by Visible Infrared Imaging Radiometer Suite (VIIRS) satellite sensor at 375 m spatial resolution starting from September 2021 [31]. An independent study used an index computed by visual inspection based anomaly detection in night time ASTER data starting from June 2021 [23].…”

Multi‐Temporal InSAR, GNSS and Seismic Measurements Reveal the Origin of the 2021 Vulcano Island (Italy) Unrest

“…The overall results presented here indicate that the investigated unrest phase (September-December 2021), that is, inflation and seismicity, together with anomalies in gasses emissions (Aiuppa et al, 2022;Federico et al, 2023;Inguaggiato et al, 2022Inguaggiato et al, , 2023, is compatible with the expansion of the hydrothermal system located within the La Fossa Caldera. Thermal anomalies also show a similar trend, with a peak again in October 2021 (Coppola et al, 2022;Corradino et al, 2023;Pailot-Bonnétat et al, 2023). While the thermal anomalies have been interpreted as an increase in temperatures of the fumarolic field present in the crater area of the La Fossa cone, the geochemical anomalies are interpreted as an increase in the parameters of the hydrothermal system which in turn is enriched in a strong and deep input of fluids released from an underlying magma batch (Aiuppa et al, 2022;Inguaggiato et al, 2022).…”

“…Since September 2021, Vulcano has undergone a new phase of unrest. Fumarolic activity increased in the latter half of September, accompanied by intensified seismic activity (Coppola et al., 2022; Corradino et al., 2023; Federico et al., 2023; Inguaggiato et al., 2023). Notably, Very Long Period (VLP; frequency peak ∼ 0.3 Hz) seismic events were recorded for the first time, with the source area located at 950 ± 270 m below sea level, North of La Fossa cone (Federico et al., 2023).…”